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Father of Ethology: Konrad Lorenz,
•A medical doctor in the German army
•Four years in a Russian POW camp
•Father of Ethology: established Max Plank Institute
Dept of Comparative Ethology
•Nobel laureate
•Author of “On Aggression” in which he argued that
even humans have innate aggressive tendancies
Father of Behavior Genetics: Walter Rothenbuhler
•Born and raised in Ohio
•Professor at OSU
•Performed critical first experiments in behavior genetics
demonstrating that two genes control hygienic behavior in
honeybees
The birth of modern behavior genetics:
American foulbrood disease in honeybees
•Caused by a spore-forming bacteria
•Highly resistant to treatment
•Spores last for years in hive products
•Can result in the death of the hive
•In the 1940’s it was discovered that some
hives could effectively manage AFB by
uncapping infected larval cells and
dragging the infected larvae out of the
colony before it became infectious
• 1960’s Rothenbhuler demonstrates that two separate and
recessive genes control uncapping and removal behaviors
•This behavior effectively controls this and a variety of other
foulbrood diseases.
Tracheal mite control behaviors in honeybees: A single a dominant gene allele
•Tracheal mites get into the trachea of honeybees lay eggs which clog
the trachea, eventually suffocating the bee.
•Bob Danka demonstrated that some bees could effectively resist the
mite
•These bees used their middle leg to groom the mites away from the
tracheae preventing infestation.
•He also found that this grooming behavior was controlled by a single
dominant gene.
Roving vs sitting fruit fly larvae:
Environmental variation can favor expression of recessive traits
•Rovers and sitters can be classified by distance they travel in a
petridish over the course of 5 min.
Roving vs sitting fruit fly larvae: A single gene case
•Crossing pure rover females with pure sitter males
results in
•F1 generation that is all rovers
•F2 generation that is 75% rovers 25% sitters
•Thus, roving behavior is produced by a classic single
dominant gene trait.
Experiment: What might happen under
high vs low population densities?
Control of behavior by only one or a few genes is relatively rare
Examples:
•Hygienic behavior in honey bees:
•One “uncapping” gene
•One “brood-removal” gene
•Grooming behavior in honey bees
•Rover vs. sitter fruit flies (1 gene)
However, most behavioral traits are polygenic: They are influenced by a large
number of genes.
Furthermore: Pleiotropy,1 gene influencing several different behavioral
phenotypes is also common in the control of behavior.
This makes it more difficult to have systematic experimental control.
Suppressed mite reproduction (SMR): Additive genetic traits
•SMR is an ability to reduce the reproductive success of varroa mites.
•Chemical
•Behavioral
•SMR is an additive trait is controlled by neither dominant or recessive
genes.
•SMR is determined by more than one gene.
•more of these genes are present, the more of the trait will be
expressed.
Natural selection and selective cross breeding
Example: garter snake preference for the banana slug
Heredity versus environment?? Nature vs nurture??
-- meaningless questions--
(1) Genes code proteins, not behavior
(2) Genes act through the environment
What is the moral of the “trading places”
story??
Coeffecient of relatedness and predictions of complex genetic influences
The coefficient of relatedness (r) between two individuals is defined as
the percentage of genes that those two individuals share by common
descent.
•MZ twins = 1.0
•DZ twins = 0.5
•Siblings = 0.5
•Parents & offspring = 0.5
•Grandparents & grand children =0.25
If a behavioral trait is under complete genetic control would we predict
that r =total variability in the trait?
Heritability:
A measure of how strongly a phenotype is influenced by genetics
Total phenotypic variation=VT=VG+VE+VI
where:
VT= total phenotypic variation observed in a (behavioral) trait
VG= variation in population due to genotype
VE =variation in population due to environment
VI = variation in population due to interaction of VG with VE
(i.e. VGxVE)
Heritability (H2)
H2=VG/(VG+VE+VI) = VG/VT
again:
VT= total phenotypic variation observed in a (behavioral) trait
VG= variation in population due to genotype
VE =variation in population due to environment
VI = variation in population due to interaction of VG with VE
and H2= heritable variance
Characteristics of H2
•Heritability is standardized variance ranging from 0.0-1.0
•Indicates what fraction of the total variance in a trait is due to variation in genes:
•H2=0: None of the variance in the trait is influenced by genes
•H2=1: All of the variance in the trait is determined by genes
Two major approaches used by behavior geneticists to study relative
contributions of genes & environment in the development of behavior
•Hold genetic make-up constant to study effects of the environment alone (VT=VE)
•cross-fostering experiments & twin studies
•Hold environment constant & explore effects of genes alone (VT=VG)
•selective breeding experiments
•use of genetic “knock-outs”
Keep in mind:
•genetic effects are usually complex, involving Pleiotropic and Polygenic effects
•Environmental effects are complex involving multiple environmental factors
•Complex genetic and environmental effects will be further complicated by
gene/environment interactions.
1 of 6 warbler species that regularly winter in the British Isles, 4 of which
are migratory Chiffchaff, Blackcap, Firecrest and Goldcrest
winter Atlas 1981-1984, estimates 3,000 Blackcaps